Low resistance fluid flow switch



W. R. WALKER AL 1,397,454

LOW RESISTANCEJELUID FLGW SWITCH Filed March a, 1931 INVENTORS W 771L900BY ATTORNEY Patented Feb. 14, 1933 UNITED STATES PATENT OFFICE WARREN B.WALKER, SHORT HILLS, AN D FRANK M008, 0]! HOBOKEN, NEW JERSEY,.ASSIGNORS '10 GENERAL ELECTRIC VAPOR LAMP COHZPANY, 0] HOBOKEN, NEW

JERSEY, A CORPORATION OF NEW JERSEY LOW RESISTANCE FLUID FLOW SWITCHApplication filed amen a, 1981. Serial Ho. 519,888.

of novel construction, and in a novel method of operating fluid flowswitches, as herelnafter set forth and claimed.

A particular object of the invention is to provide a fluid flow switchhaving a relatively large current capacity. Another object of theinvention is to provide a switch having a low internal resistance. Stillanother object of the invention is to provide a novel method ofoperating a fluid flow switch. Other objects and advantages of theinvention will appear from the following detailed specification, or froman inspection of the accompanying drawing.

The current rating of electrical switches is determined, as is welllmown, bytwo factors; the current which they can safely interrupt, andthe current which they can continuously carry without undue heating dueto the internal resistance thereof. In switches of the fluid flow typethe emphasis has been on the first of these factors, hence in this typeof switch the metallic inleads have invariably been spaced aconsiderable distance apart, in order to permit the arc of rupture to bedrawn out sufliciently to extinguish it. This construction obviouslynecessitates the use of a relatively long fluid path to complete thecircuit through the switch when it is in a closed circuit position. Along fluid path is, however, highly undesirable from the standpoint ofthe second factor mentioned above, due to the fact that any of thefluids .which are ordinarily used have a relatively high specificresistance. For example, mercury, the fluid almost universally'used, hasa specific resistance which is approximately twenty times that oftungsten, and sixty .timesthat of copper. Hence from the standpoint ofminimum internal resistance, and thus "of minimum heating, it'is obviousthat thefluid path between the inleads should be as short as possible,especially since the eifective conducting area of the fluid path islimited by practical considerations, such as maximum dimensions for theswitch, weight, cost, and the like. It would thus appear that additionalcurrent carrying capacity could be obtained in a practical switch onlyby a sacrifice of the rupturing capacity, with the result that there hasbeen heretofore a more or less definite limit to the capacity ofcommercially practical switches. I

' We have now discovered that this limitation can be overcome by meansof a novel construction of our invention, which operates in a uniquemanner to give a minimum fluid path when the switch is in the closedcircuit position without necessitating any corresponding reduction ofthe path of the arc of rupture. According to our new invention thecircuit is opened or closed by fluid flow in a conventional mannerbetween widely separated fluid pools. The fluid movement is availed of,however, to move a solid metallic conductor which is located within theswitch envelope in such a manner that the length of the fluid path whichmust be traversed by the current is materially reduced after the circuitthrough the switch has been closed, and increased again before thecircuit through the switch is opened. Consequently our new Fig. 1 is asectional view of a mercury switch having a bridging conductor operatedby a float, said switch being shown in an open circuit position,- andFig; 2is a sectional view of the same switch in a closed circuitpositlon.

In the drawiu the tubular sealed envelope f 1 may'consist 0 any suitablevitreous material, suoh as glass, fused silica, or the like, but Iprefer to use a borosilicate glass, due both to the refractory nature ofthis glass and the ease with which inleads are sealed therein. At oneend of said envelope there is a re- A fractory body 2 of porcelain,lavite, or the like, said body having a cup 3 formed therein at the endwhich is nearer the adjacent end of the envelope 1. A channel 4 in thetop of said refractory body 2 extends from said cup 3 to the other endof said body, the bottom.

thereof sloping away from said cup. An inlead 5 is sealed through thetop of the envelope 1 at a point directly above the cup 3, said inleadextending to the bottom of said cup at a point as near the end of therefractory body 2 as is convenient, whereby said refractory body ismaintained in a fixed position within the envelope 1. A second inlead 6is sealed into the opposite end of said envelope 1 and extendslongitudinally along the bottom thereof to a point near the refractorybody 2, at which point it extends upwardly a short distance. At anintermediate point on said inlead 6 there is alsoanother upwardextension 7. A conductor 8 in the form of an inverted U has one endthereof pivotally mounted on the upturned end of the inlead 6, saidconductor having such dimensions that the other end thereof can beinserted in the cup 3 and removed therefrom at will by pivotal movementon said inlead. A lever 9 is pivotally mounted at the upper end of theextension 7 of the inlead 6. One end of said lever 9 carries a suitablefloat 10, which is preferably a hollow metal sphere, while the other endof said lever engages an arm 11 on the conductor 8 by means of asuitable pin and slot connection therebetween. A quantity of mercury 12is provided within the envelope 1 which is sufficient to so elevate thefloat 10 that the free end of the conductor 8 is raised an appreciabledistance above the levelthereof before said mercury 12 separates fromthe mercury pool 13 which is retained in the cup 3 when said switchenvelo eis tilted. When the envelope 1 is made 0 a borosilicate glass Ican conveniently use tungsten for the inleads 5 and 6, since tungstencan be fused di rectly thereto. In order to reduce the internalresistance of my switch,however, especially when very large currents areto be carried,I prefer to make that portion of the inlead 6 whichextends within the envelope 1, as well as the conductor 8, of a betterelectrical conduc tor such as copper. Since the latter metal rapidlycontaminates the mercury I find it advisable to electroplate these partswith nickel, chromium, or other metal which resists amalgamation. Theremaining metal parts, which are not called upon to carry current, may

be made of any metal which will not deleteriously affect the mercury,such as iron,

nickel or various alloys thereof, or which is plated with nickel,chromium, or the like.-

A hydrogen or other arc suppressing atmosphere iss preferably sealedwithin the en velope 1.

In the use and operation of this switch, assuming it to be in an opencircuit position,

as shown in Fig. 1, as the envelope 1 is tilted in a counter-clockwisedirection the level of the mercury 12 rises in the channel 4 until saidmercury merges with the mercury pool 13. A circuit is thereupon closedfrom the inlead 5 through a relatively long path in the mercury 12 tothe end of the inlead 6.

This circuit, which is typical of the switches it becomes immersed inthe mercury 12 at a point very close to the inlead 5, as shown in Fig.2. Due to the extremely low resistance of the conductor 8 the largerpart of the current will thereupon flow from the inlead 5 through anextremely short path of large area in the mercury 12 to the conductor 8,and thence through said conductor to the inlead 6. Since the pivotalconnection be- .tween the conductor 8 and the inlead 6 is immersed inthe mercury 12 it is obvious that a good electrical connectionwill-always exist therebetween. Hence the internalv resistance of theswitch is very materially reduced, to say a small fraction of itsoriginal I value, once the conductor 8 has become effective, with theresult that exceptionally large currents can be continuously carriedthereby. Upon'tilting the switch envelope in the reverse direction themercury 12 flows toward the float 10, causing it to-rise. The

free end of the conductor, being linked to said float, necessarily risestherewith, and soon moves out of contact with the mercury 12. No arc ofrupture ensues, however, since a circuit is still closed between theinleads 5 and 6 through a longer mercury path, with the result that saidmercury 12 is maintained at substantially the same-potential as theconductor 8. Further tilting of the envelope 1 in a clockwise directioncauses the mercury '12 to flow away from the cup 3, until it eventuallyseparates from the mercury pool 13 therein whereupon the circuit throughthe switch is interrupted. The-arc of rupture which thereupon occurs isdrawn out by the flow of the mercury 12 into the channel 4, where it issoon suppressed by the hydrogen atmospher. The conductor 8 having been.elevated to a"considerable height above the levellof the mercury 12before this are free end of the conductor 8 is continued until ofrupture occurs there is no likelihood of the are striking thereto.. Withthis construction it is obvious that the rupturing capacity of theswitch is not in any way impaired,

despite the provision of the short fluid path during the time that theswitch is closed. As a result currents well in excess of amperes may besuccessfully handled by a switch of our novel construction, and operatedin the manner of our invention, of a size com-, mensurate with 25 ampereswitches of the type heretofore in use.

While we have described our invention by reference to a specificconstruction it is obvious that our invention is not limited thereto,but that various changes, omissions and substitutions, within the scopeof the appended claims, may be made therein without departing from thespirit thereof.

lVe claim as our invention:

1. A fluid flow switch comprising a sealed envelope, two inleads sealedtherein, a fluid conductor in said envelope, a movable solid conductorwithin said envelope, and means responsive to movement of said fluidconductor to move said movable conductor.

2. A fluid flow switch comprising a sealed envelope, two inleads sealedtherein, a fluid conductor in said envelope, a movable solid conductorwithin said envelope, and means responsive to movement of said fluidconductor to move said movable conductor to change the length of thefluid path between said inleads.

3. A fluid flow switch comprising a sealed envelope, two inleads sealedtherein, a fluid conductor in said envelope, a movable solid conductorwithin said envelope, and means responsive to movement of said fluidconductor to move said movable conductor into a bridging positionbetween said inleads after the pircuit has been closed therebetween bysaid fluid conductor, and out of said bridging position before thecircuit is opened therebetween.

4. A fluid flow switch comprising a sealed envelope, two inleads sealedtherein, a fluid conductor in said envelope, a bridging member pivotallymounted on one of said inleads, and means responsive to movement of saidfluid conductor to move the free end of said bridging member intocontact with said fluid at a point in juxtaposition to the other of saidinleads. v

5. A mercury switch comprising a sealed envelope, mercury in saidenvelope, two inleads sealed into said envelope, each of said inleadsterminating in a pool of said mercury, a bridging member pivotallysupported by one of said inleads, and means responsive to movement ofsaid mercury to move the free end of said bridging member into con tactwith said mercury at a point in juxtaposition to the other of saidinleads after said pools have been merged by mercury flow and to removesaid free end from contact with said mercury before said pools separate.

6.. A mercury switch comprising a sealed whereby the free end of saidbridging member is caused to move in accordance with changes in thelevel of said mercury.

7. A mercury switch comprismg a sealed envelope, mercury in saidenvelope, two inleads sealed into said envelope, each of said inleadsterminating in a pool of said mercury, a bridging member pivotallysupported by one of said inleads and a float operated lever supported bysaid inlead and linked with said bridging member" in such a manner thatthe free end of said bridging member is moved into contact with saidmercury ata point in juxtaposition to the other inlead whenever saidmercury rises above the level at which said pools are merged, and out ofcontact with said mercury whenever said mercury falls toward the levelat which said pools separate, the pointof support of said bridgingmember being located at a point which is below the level of. the mercurywhenever the free end thereof is in contact with said mercury.

Signed at Hoboken in the county of Hudson and State of New Jersey this2nd day of March A. D. 1931. v

Y WARREN R. WALKER.

FRANK MOOS.

